[Pw_forum] Dielectric constant with Lyddane-Sachs-Teller relation

[TuanAnh Pham]

Dear Paolo,

Thank you very much for your suggestion.

Best regards,
Tuan Anh.

On Tue, Jan 13, 2009 at 9:15 AM, Paolo Giannozzi <giannozz at democritos.it>wrote:

> TuanAnh Pham wrote:
>
> > Could you please let me know what is the different between
> > these two methods ?
>
> they should give the same results, when both methods apply
>
> > Is that correct that the LST relation only works for the system with
> > sufficient symmetry?
>
> typically the LST relation is derived for high-symmetry crystals
> with two atoms in the unit cell, in which all you have is one TO
> and one LO nonzero frequency at Gamma. The LST relation can be
> generalized, though. See for instance this old paper:
> W. Cochran and R. A. Cowley, J. Phys. Chem. Solids 23, 447 (1962)
>
> Paolo
> --
> Paolo Giannozzi, Democritos and University of Udine, Italy
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>



-- 
Tuan Anh Pham
Graduate Student
University of California, Davis
Phone: 530-752-0957
Homepage: http://angstrom.ucdavis.edu/
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20090115/891557e6/attachment.html>